Rheostat



RHEOSTAT Filed Nov. 1923 In ven/tor y Patented Aug.. 23, 1927.

PoWEL cRosLEY, Jn., or CINCINNATI, onro.

Application led November 3, 1923. Serial No. 672,492.

My invention relates to rheostats, and more particularly to those for use in 'circuits of low voltage, as in radio receiving apparatus or any other apparatus where a large number of relatively small variations of resistance are required, to afford appreciable variation of current with such low voltage.

The object of my invention is to provide a simple, compact and inexpensive rheosta-t,

o easy to install, especially under the conditions encountered in supplying parts of apparatus to various users who assemble them variously to suit their own purposes. A further object is to provide, in one simple apparatus, for increasing' resistance at a rela` tively slow rate, and also for increasing resistance at a relatively rapid rate, to make the device suitable for regulating the operation of apparatus, such as the vacuum tubes of radio apparatus, of diferent makes. An other object, preferably, is to insure durability against mechanical wear and heating as well as other electrical effects. Other objects will appear in the course of the ensuing descriptimio l attain these objectsv by the device illustrated, 'for example, in the accompanying drawing, in which- Figure 1 is a rearl or inside elevation, parts 3o of .the support and connections being shown, and the rheostat being adjusted to a, point about half way of its range of adjustment;

2 is an upright` section on' the plane of the broken line 2 -2 of lig, 1; 4 3 is an enlarged fragmentary view, with the` pitch of the coils exaggerated, to

rillustr'ate the connection of two sections of the coil;

Fig. 4 is a detail perspective view of the radial connector; and y Fig. 5 is a similar view of the central spring.

The core 1 is curved into an almost/com- Y plete circle with ends almost meeting, and its cross-section is. that of a flat rectangle with its lesser dimension radial to the curv# ing, presenting one broad side inward. Its

spaced turns, usually a little fart-her apart than the diamcterof the wire.

The free end of the second wire 3 is passed through a hol-e in the core 1 some distance from one end of the core and is clinched or otherwise suitably secured, without electrical connection to any other conductor; and the opposite end of the first wire 2 is passed through a hole about the same distance from the opposite end of the core 1, from the outer to the inner side, and has its end clamped under the head of the terminal screw 4 passing out through the core near this end.

The mounting is a shallow cup 5 with insulating surface and preferably made entirely of insulating material, such as porcelain, har-d rubber, liber or the like; and the core 1 with its wires 2 vand 3 wound thereon, fits snugly in this cup. The opposite end of the core 1 has the other terminal screw 6 passing out through it; and the rim of the cup 5 has recesses 7 receiving these screws 4 and 6, which have nuts 8 on their respective outer parts, clamping tightly against the outside of the cup and thus holding the core and its windings in the cup.

Additional nuts 9 on the screws 4 and 6 clamp suitable connectors 10 against the nuts 8; it being understood that any desired conductors may be attached to these connectors for including the rheostat in a circui The shaft ll'passes cent-rally through the cup 5 and through the panel 12 on which' the cup 5 is mounted by means of a flatheaded screw 13 passed in through the panel and cup, with a nut 14 against the inner side of the cup. lfiixed on the outer end of the shaft 11 is the knob 15. Inside, the radial connector 16 has a circular end part 17 with a central opening through which the shaft 11 extends, and a foot 18 with an opening through which the second terminal screw 6 passes, clamping this foot to the inside of the cup rim.,

The central spring 19 is a disk of resilient metal having a central opening through which the shaft 11 passes, and havingl a series of recesses 2() in its periphery and being concave out Atoward the adjacent part 17 of the connector 16', the peripheral sections .left between the recesses 20 acting as spring llO arms uniformly distributed around the shaft l1. v y

The guide arm 2l is cylindrical, with the shaft 11 passing diametrically through it l onvth'e shaft. The contact element 23 comp rises the convex head 24 and a stem 25 fitting slidingly in a bore in the outer end vof the guide arm 21, with a small coil spring 26 confined by the end of this stem, against the end of the bore; the spring 26 thus forcing the element 23 out so that its rounded head 24 bears against the inner stretches hole 27 being made in the core 1, and the ends of the two wires 2 and 3 being passed inward through this hole, then around the edges of the core l around which they respectively just previously passed, bringing both ends of the wires to the outside, where they are twisted together as at 28; the twisted together ends then being bent down alongside the corel between the adjacenti stretches of wire, where they will be confined by the rim of the cup 5 when the parts are assembled as before described.

By having the Wires 2 and 3 of the same cross-section, or approximately the same, the device operates more uniformly, mechanically, and has a neater appearance, than if there were a considerable difference in sizes of the wires to obtain a decided difference in rate of resistance increase per turn of wire traversed by the Contact element 23, which rate, in the two wires 2 and 3, in the present device, is provided by utilizing a diiierent metal or alloy for each wire 1 and 2. As shown, the rst wire 2 is considerably shorter than the second wire 3, in accordance with requirements for use with two different kinds of vacuum tubes; the first Wire 2 being suiiicient for a tube of relatively low resistance, in proportion to which a comparatively short length of wire of low specilic resistance aords ample variation, and all that is necessary, if a tube of relatively high resistance is substituted, is to advance the contact element 23 over onto the second wire 3 as far as may be needed, to increase the resistance at a more rapid rate, in proportion to the high resistance of the substituted tube.

Modifications of the construction, or of the proportions, as of the lengths of the wires, may occur; and it will be seen that more than two wires may be combined, each having a different specific resistance, if de? quired. Other modifications may occur, and therefore I do not wish to be understood as being limited to the precise example herein disclosed, but having thus fully described my invention, what I claim as new and ldesire to secure by LettersV Patent is:

l. In a rheost-at, a curved supporting core, a plurality of resistance-wires coiled around said core, connected in series, one of said wires being of specific resistance different from that of another one of said wires, and a movable contact elementl making direct contact with successive coils of said wires.

2. In a rheostat, a curved supporting core, a plurality of resistance wires coiled around said c ore, having adjacent end parts inserted through said core and secured together at the outer or convex side of said core whereby said wires are connected in series, one of said wires being of specific resistance different-from that of another one `of said wires, and a movable contact element making direct contact with successive coils of said wires along the inner or concave side of said core.

3. In a rheostat, a curved supporting core, a plurality of resistance wires coiled around said core, having adjacent end parts inserted inward through said core 'and then passed around opposite edges of said core and secured together at the outer or convex side of said core-whereby said wires are connected in series, one of said wires being of specific resistance `different from that of another one of said wires, and a movable Contact element making direct contact with successive coils of said wires along the inner or concave side of said core.

4. In a rheostat, a plurality of resistance elements stationarily connected in series, one of said elements being of speciic resistance different from that of another one of said elements, and movable means for including various proportions of said one of said elements in a, circuit, or all ofsaid element and various proportions of said other element in the circuit.

5. In a rheostat, a plurality of resistance elements stationarily connected in series, one of said elements being of specific resistance diferent from that of another one of said elements, but both of these elements being of substantially equal cross-sectional area, and movable means for including various proportions of said one of said elements in a circuit, or all of said element and various proportions of said other element in the circuit.

rowEL' cRosLEY, JR. 

